The Department of Cell Biology Confocal Core serves a large and strong department which ranks in the top ten among all United States medical school cell biology departments for NIH funding. The department has 28 faculty members, 22 research faculty members, and 29 jointly-appointed faculty members, most of whom use confocal imaging. The Core also provides imaging for the Cancer Center, and for other departments that lack their own dedicated confocal imaging capability. The only confocal microscope in the core is more than 11 years old and will not long be supported by the manufacturer. We request funds to replace the existing instrument with a state-of-the-art laser scanning confocal microscope suitable for an imaging core with a large number of users having diverse needs. We have chosen the Leica SP5 AOBS, a laser scanning confocal microscope that will provide maximal technical capability while requiring the least retraining of our large population of existing users. Confocal microscope technology has made major advances in the last decade. We will bring these newer technologies, and the experimental techniques they enable, to our large base of NIH-funded researchers.